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Greenhouse, conservatory and houseplants

Houseplants

Cacti and Clivia houseplants should still be kept dormant until March. Very little water (barely moist) and no feeding is advised until then. Clivia will additionally benefit from lower light levels (e.g. a back room where the lights are rarely turned on and there is not too much natural light) - this will improve flowering for the following season.

Deadhead Hippeastrum (amaryllis) leaving the flower stalk to die down naturally. Keep feeding and watering and you may be treated to further flowers in August as well as the normal blooms next winter.

Keep Cyclamen in a cool, well-lit place and water them from below (into the saucer). Allow the plant to drink for half an hour, before pouring away the remaining water left in the saucer. If the level in the saucer does not go down, then the plant did not need a drink. You can always tip out the rootball and feel it before watering, to see if the compost is dry, or if it is still moist from previous watering. If the leaves on pot Cyclamen start to turn yellow this may be a sign of overwatering.

Citrus trees in pots should be top-dressed with fresh compost, and/or repotted if necessary.

Cool conditions and regular watering will help keep potted indoor azaleas looking good for longer. Remember to water azaleas with rainwater collected in a rain butt, not with tap water.

Indoor forced bulbs that were in the house for winter displays, but which have now finished flowering, can be left outside in a sheltered spot in the garden to finish dying down.

General houseplant care

Don't leave houseplants on windowsills behind the curtains on frosty nights, especially if your windows are not double-glazed.

Stand houseplants on trays of damp gravel to counteract drop in humidity in centrally-heated homes.

Water houseplants sparingly until they come into active growth with the advancing spring.

Check that light levels are sufficient for houseplants. They will need light to carry on until the spring, and can easily be forgotten in a back or spare room that receives little natural light, or with the curtains left drawn. They are best moved to sunny positions until March.

Pruning and training

Plumbago, passion flower and jasmine can be thinned out, so that they have a neat framework of branches. The previous year’s growth can also be cut back to two or three buds from the main framework, to keep the size under control.

Bougainvillea pruning is sometimes left until early spring the year after flowering, because of the risk of frost damage when pruning in the autumn, just after flowering. Last year’s growth should be spur-pruned back to 2.5cm (1in) of the main woody framework. Do not prune unless the glasshouse or conservatory is reliably above 10°C (50°F).

Schlumbergera truncata and S. x buckleyi (Christmas cactus) - twist off some of the stem segment, with a view to keeping a balanced shape to the plant. This will encourage bushy growth. The detached segments can be used as cuttings, if dried and kept warm for a week, before potting up in gritty compost.

Cut back leggy Hypoestes (polka dot plant), Pilea (aluminium plant), Coleus (now called Solenostenum), Tradescantia, Pelargonium, Salvia, Argyranthemum and Lantana to encourage new growth and keep the plants well shaped. Prunings can always be used as softwood cuttings.

In the greenhouse

Fuchsias can be started into active growth (if not done last month) by repotting, increasing watering, feeding (with a slow-release fertiliser such as blood, fish and bone), and putting them in a sunny place. Those that were started up in January can now be sprayed with water occasionally to raise humidity, encourage growth, and help bud break.

Greenhouse bulbs that have finished flowering (e.g. freesias and Lachenalia) can now be fed weekly with high potassium feed (such as tomato fertiliser), to build up the bulbs before resting them over the summer. Reduce feeding and watering as the foliage starts to die back, and then lay the pots on their sides under the greenhouse bench until next autumn.

Begonia, Gloxinia and Achimenes tubers can all be planted this month. Begonias and gloxinias need to be planted hollow side upwards; Achimenes can be planted on their sides, in trays if necessary, before potting them on as necessary once growth appears.

Propagation

If you do have any seedlings and/or cuttings in the greenhouse, make sure they are getting the maximum light available, or else they will become weak and leggy. If necessary, turn them once a day so that they get light on both sides. This will stop them leaning over towards the light, and keep them upright and compact.

Plug plants are now available for sale. They can be grown on in your glasshouse, being a relatively cheap source of large numbers of plants, while avoiding the need for propagation facilities and labour.

Pest and disease watch

Fungal diseases

Ventilating the glasshouse or conservatory on mild sunny days will help to reduce fungal infections.

Regularly pick over plants and sweep up fallen debris, to prevent disease spreading.

Cyclamen persicum (often given as a winter pot plant) is best watered from below (i.e. into the saucer, not the pot), as wetting the leaves can easily result in fungal infections such as cyclamen grey mould and rotting off.